System for using constricted convection with closed loop cooling system as the convection plate

ABSTRACT

A gas cooling system for an electronic display is disclosed herein. A closed loop of circulating gas is preferably positioned to surround the electronic display. An open loop of cooling air preferably travels along the rear surface of the electronic display. In an exemplary embodiment the cooling air does not mix with the circulating gas. Heat may be transferred from the circulating gas to the cooling air in order to cool the display.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/508,767 filed on Oct. 7, 2014, now U.S. Pat. No. 9,089,079 issuedJul. 21, 2015. U.S. application Ser. No. 14/508,767 is a continuation ofU.S. application Ser. No. 13/937,777 filed on Jul. 9, 2013, now U.S.Pat. No. 8,854,572 issued Oct. 7, 2014. U.S. application Ser. No.13/937,777 is a continuation of U.S. application Ser. No. 13/605,530filed on Sep. 6, 2012, now U.S. Pat. No. 8,482,695 issued Jul. 9, 2013.U.S. application Ser. No. 13/605,530 is a continuation of U.S.application Ser. No. 12/620,330 filed on Nov. 17, 2009, now U.S. Pat.No. 8,274,622 issued Sep. 25, 2012, which is a non-provisionalapplication of U.S. Application No. 61/115,333 filed Nov. 17, 2008. U.S.application Ser. No. 12/620,330 is also continuation-in-part of U.S.application Ser. No. 12/411,925 filed Mar. 26, 2009, now U.S. Pat. No.8,854,595 issued Oct. 7, 2014, which is a non-provisional application ofU.S. Provisional Application No. 61/039,454 filed Mar. 26, 2008. U.S.application Ser. No. 12/620,330 is also a continuation-in-part of U.S.application Ser. No. 12/556,029 filed Sep. 9, 2009, now U.S. Pat. No.8,373,841 issued Feb. 12, 2013, which is a non-provisional applicationof U.S. Provisional Application No. 61/095,615 filed Sep. 9, 2008. U.S.application Ser. No. 12/620,330 is also a continuation-in-part of U.S.application Ser. No. 12/234,307 filed Sep. 19, 2008, now U.S. Pat. No.8,767,165 issued Jul. 1, 2014, which is a non-provisional application ofU.S. Provisional Application No. 61/033,064 filed Mar. 3, 2008. U.S.application Ser. No. 12/620,330 is also a continuation-in-part of U.S.application Ser. No. 12/234,360 filed Sep. 19, 2008, which is anon-provisional application of U.S. Provisional Application No.61/053,713 filed May 16, 2008. U.S. application Ser. No. 12/620,330 isalso a continuation-in-part of U.S. application Ser. No. 12/237,365,filed Sep. 24, 2008, now U.S. Pat. No. 8,879,042 issued Nov. 4, 2014,which is a non-provisional application of U.S. Provisional ApplicationNo. 61/057,599 filed May 30, 2008. U.S. application Ser. No. 12/620,330is also a continuation-in-part of U.S. application Ser. No. 12/235,200filed Sep. 22, 2008, which is a non-provisional application of U.S.Provisional Application No. 61/076,126 filed Jun. 26, 2008. Allaforementioned applications are hereby incorporated by reference intheir entirety as if fully cited herein.

TECHNICAL FIELD

Exemplary embodiments generally relate to cooling systems for electronicdisplays.

BACKGROUND OF THE ART

Conductive and convective heat transfer systems for electronic displaysare known. These systems of the past generally attempt to remove heatfrom the electronic components in a display through as many sidewalls ofthe display as possible. While such heat transfer systems have enjoyed ameasure of success in the past, improvements to displays require evengreater cooling capabilities.

In particular, cooling devices for electronic displays of the past havegenerally used convective heat dissipation systems that function to coolan entire interior of the display by one or more fans and fins, forexample. By itself, this is not adequate in many climates, especiallywhen radiative heat transfer from the sun through a display windowbecomes a major factor. In many applications and locations 200 Watts ormore of power through such a display window is common. Additionally,modern applications call for larger displays than previous applications.For example, some outdoor applications call for forty-seven inch screensand above. With increased heat production from the larger screens andradiative heat transfer from the sun through the display window, moreefficient and powerful heat dissipation systems are required.

SUMMARY OF THE EXEMPLARY EMBODIMENTS

A large fluctuation in temperature is common in the devices of the past.Such temperature fluctuation adversely affects the electronic componentsin these devices. Whereas the systems of the past attempted to removeheat only through the non-display sides and rear components of theenclosure surrounding the electronic display components, a preferredembodiment causes convective heat transfer from the face of the displayas well. By the aspects described below, exemplary embodiments have madeconsistent cooling possible for electronic displays having screens ofsizes greater than or equal to twelve inches. For example, cooling of a55 inch screen can be achieved, even in extremely hot climates. Greatercooling capabilities are provided by the device and method described andshown in more detail below.

An exemplary embodiment relates to an isolated gas cooling system and amethod for cooling an electronic display. An exemplary embodimentincludes an isolated gas cooling chamber. The gas cooling chamber ispreferably a closed loop which includes a first gas chamber comprising atransparent anterior plate and a second gas chamber comprising a coolingplenum.

The first gas chamber is anterior to and coextensive with the viewableface of the electronic display surface. The transparent anterior platemay be set forward of the electronic display surface by spacers definingthe depth of the first gas chamber. A cooling chamber fan, or equivalentmeans, maybe located within the cooling plenum. The fan may be used topropel gas around the isolated gas cooling chamber loop. As the gastraverses the first gas chamber it contacts the electronic displaysurface, absorbing heat from the surface of the display. Because the gasand the relevant surfaces of the first gas chamber are transparent, theimage quality would preferably remain excellent. After the gas hastraversed the transparent first gas chamber, the gas may be directedinto the rear cooling plenum.

In order to cool the gas in the plenum, external convective orconductive means may be employed. In at least one embodiment, anexternal fan unit may also be included within the housing of thedisplay. The external fan unit may be positioned to provide a flow ofingested air over the external surfaces of the plenum. The heated air inthe housing may exit the housing as exhaust.

The two chambers of the closed loop plenum encircle the electronicdisplay. Within electronic displays is typically a backlight, especiallyin liquid crystal displays (LCD). The backlight can be a significantsource of heat for the electronic display. Exemplary embodimentsposition the backlight sufficiently close to the wall of the coolingplenum so that convective heat transfer from the backlight can beincreased. The external fan may force air between the plenum and thebacklight or air may be pulled from the top of the display using anadditional fan unit. Alternatively, a combination of both fans may beemployed.

The foregoing and other features and advantages of the present inventionwill be apparent from the following more detailed description of theparticular embodiments of the invention, as illustrated in theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of an exemplary embodiment will be obtained froma reading of the following detailed description and the accompanyingdrawings wherein identical reference characters refer to identical partsand in which:

FIG. 1 is an exploded perspective view of an exemplary embodimentshowing components of the isolated gas cooling system.

FIG. 2 is top sectional view of an exemplary embodiment of the coolingchamber.

FIGS. 3A-3E are cross sectional views of exemplary embodiments usingconstricted convection cooling.

DETAILED DESCRIPTION

FIG. 1 is an exploded view of an exemplary embodiment of the closed loopcooling system. This system is fully described in co-pending U.S.application Nos. 61/033,064 and 61/053,713 herein incorporated byreference in their entirety.

It is to be understood that the disclosed embodiments includes thecooling of displays including, but not limited to LCDs. By way ofexample and not by way of limitation, the exemplary embodiments may beused in conjunction with displays selected from among LCD (including TFTor STN type), light emitting diode (LED), organic light emitting diode(OLED), field emitting display (FED), cathode ray tube (CRT), and plasmadisplays. Furthermore, embodiments may be used with displays of othertypes including those not yet discovered. In particular, it iscontemplated that the exemplary embodiments may be well suited for usewith full color, flat panel OLED displays. While the embodimentsdescribed herein are well suited for outdoor environments, they may alsobe appropriate for indoor applications (e.g., factory environments)where thermal stability of the display may be at risk.

An exemplary embodiment 10 of the electronic display and gas coolingsystem includes an isolated gas cooling chamber 20 contained within anelectronic display housing 70. A narrow transparent first gas chambermay be defined by spacers 100 and transparent front plate 90. A secondtransparent front plate 130 may be laminated to front plate 90 to helpprevent breakage of transparent plate 90. Cooling chamber 20 surroundsan electronic display 80 (in this case an LCD stack) and associatedbacklight panel 140 (although some embodiments may not require abacklight panel).

The gas cooling system 10 may include means for cooling gas containedwithin the cooling plenum 45. This means may include a fan 60 which maybe positioned at the base of the display housing 70. The fan will forcethe cooler ingested air over at least one external surface of aposterior cooling plenum 45. If desired, an air conditioner (not shown)may also be utilized to cool the air which contacts the external surfaceof plenum 45. This air may be the same air that is forced between thebacklight 145 and the surface of the plenum 45 in order to further coolthe backlight 145.

Referring to FIG. 2, in at least one embodiment the isolated gas coolingchamber 20 comprises a closed loop which includes a first gas chamber 30and a rear cooling chamber 40. The first gas chamber includes atransparent plate 90. The second gas chamber comprises a cooling plenum45. The term “isolated gas” refers to the fact that the gas within theisolated gas cooling chamber 20 is essentially isolated from externalair in the housing of the display. Because the first gas chamber 30 ispositioned in front of the display image, the gas should besubstantially free of dust or other contaminates that might negativelyaffect the display image.

The isolated gas may be almost any transparent gas, for example, normalair, nitrogen, helium, or any other transparent gas. The gas ispreferably colorless so as not to affect the image quality. Furthermore,the isolated gas cooling chamber need not necessarily be hermeticallysealed from the external air. It is sufficient that the gas in thechamber is isolated to the extent that dust and contaminates may notsubstantially enter the first gas chamber.

The first gas chamber 30 is in gaseous communication with the rearcooling chamber 40. A cooling chamber fan 50 may be provided within theposterior plenum 45. The cooling fan 50 may be utilized to propel gasaround the isolated gas cooling chamber 20. The first gas chamber 30includes at least one transparent plate 90 mounted in front of anelectronic display surface 85. The transparent plate 90 may be setforward from the electronic display surface 85 by spacers 100. Thespacing members 100 define the depth of the narrow channel passing infront of the electronic display surface 85. The spacing members 100 maybe independent or alternatively may be integral with some othercomponent of the device (e.g., integral with the front plate). Theelectronic display surface 85, the spacing members, and the transparentfront plate 90 define a narrow first gas chamber 30. The chamber 30 isin gaseous communication with plenum 45 through entrance opening 110 andexit opening 120.

FIG. 3A shows a cross-sectional view of the section that is shown inFIG. 2. Towards the front of the display is the first gas chamber 30which abuts against the electronic display 80. In front of the first gaschamber 30 is the transparent plate 90. Towards the rear of the display,the backlight 140 is placed in close proximity to the posterior rearcooling chamber 40. The close proximity of these two elements, in part,creates the constricted convection cooling of the backlight 140. One ormore constricted convection fans 200 may be used to draw air between thebacklight 140 and the rear cooling chamber 40. It has been found thatforcing air through a smaller space increases the cooling abilities ofthe system. The distance between the backlight 140 and the rear coolingchamber 40 may vary depending on many factors, including but not limitedto: the size of the display, the design of the backlight assembly, thedesired operating environment, and the size and speed of the selectedconstricted convection fans. An ideal distance may be between 0.25 and1.25 inches. Alternatively, an ideal distance may be between 0.33 and2.5 inches. Larger distances may be preferable, depending at least uponthe many factors listed above.

The backlight may comprise a printed circuit board (PCB) with aplurality of lights mounted to the side facing the electronic display80. The lights in the backlight may be any one of the following: LED's,organic light emitting diodes (OLED), field emitting display (FED),light emitting polymer (LEP), or organic electro-luminescence (OEL)lights. In an exemplary embodiment, the backlight 140 would ideally havea low level of thermal resistance between the side facing the electronicdisplay 80 and the side facing the cooling plenum. To accomplish thislow level of thermal resistance, the backlight 140 may be built usingmetal printed circuit board (PCB) technology to further transfer heataway from the lights. The rear surface of the backlight 140 may also bemetallic, or some other thermally conductive material, to furtherenhance the convective heat transferring properties. The surface mayeven have a plurality of surface features such as fins to furtherenhance the convective heat transferring properties. The constrictedconvection fan 200 may then send the warm air out of an exhaust 179(shown in FIG. 1) so that it may exit the display housing entirely.

FIG. 3B shows another cross-sectional view of another embodiment for theconstricted convection setup. In this embodiment, the constrictedconvection fan 200 is used to push air between the backlight 140 and therear cooling chamber 40. FIG. 3C shows an embodiment without theconstricted convection fan, but instead uses the fan 60 which draws airfrom outside the display housing. As noted above, this air may simply beambient air or alternatively this air may come from a conditioning unit(not shown). To facilitate the flow of air between the backlight 140 andthe rear cooling chamber 40, a guiding device 210 may be used.

FIG. 3D shows another embodiment, where the rear cooling chamber 40contains a guiding feature 41, which is used in combination with theguiding device 210 to facilitate the flow of air between the backlightand the cooling chamber. FIG. 3E shows another embodiment, where boththe fan 60 and the constricted convection fan 200 is used. Thisembodiment could also utilize a version of the guiding devices shown inFIGS. 3C and 3D.

While the display is operational, the fan 60 and the constrictedconvection fan 200 may run continuously. However, if desired, atemperature sensor (not shown) and a switch or microcontroller (notshown) may be incorporated within the electronic display. This effectivethermostat may be used to detect when temperatures have reached apredetermined threshold value. In such a case, the various fans may beselectively engaged when the temperature in the display reaches apredetermined value. Predetermined thresholds may be selected and thesystem may be configured with a thermostat (not shown) to advantageouslykeep the display within an acceptable temperature range. This would saveon both energy costs as well as the useful lifetime of the devices.

An optional air filter (not shown) may be employed within the plenum toassist in preventing contaminates and dust from entering the first gaschamber 30. An air filter could also be used to prevent fan 60 fromdrawing in particulates from either the surrounding environment or theconditioning unit.

It should be noted, that some embodiments may not use display technologythat requires a backlight. For these types of displays, the electronicdisplay 80 would be placed anterior to the rear cooling chamber 40(rather than the backlight 140). For example, an OLED may be placedanterior to the rear cooling chamber 40 so that cooling air could beforced between the posterior surface of the OLED and the rear coolingchamber 40.

Having shown and described the preferred embodiments, those skilled inthe art will realize that many variations and modifications may be madeto affect the embodiments and still be within the scope of the claimedinvention. Additionally, many of the elements indicated above may bealtered or replaced by different elements which will provide the sameresult and fall within the spirit of the claimed invention. It is theintention, therefore, to limit the invention only as indicated by thescope of the claims.

I claim:
 1. A gas cooling system for an electronic display having adisplay surface and a rear surface, the system comprising: a closed loopof circulating gas positioned to surround the electronic display; and anopen loop of ambient gas which contacts the rear surface of theelectronic display; where the circulating gas and ambient gas are twoseparate flows of fluid.
 2. The system of claim 1 further comprising: ameans for transferring heat from the circulating gas to the ambient gas.3. The system of claim 2, wherein: the means for transferring heat fromthe circulating gas to the ambient gas comprises placing the circulatinggas within a plenum and allowing ambient gas to contact exteriorsurfaces of the plenum.
 4. The system of claim 1, further comprising: atransparent anterior plate positioned in front of the display surface todefine a gap; a fan positioned to force the circulating gas through saidgap.
 5. The system of claim 4, further comprising: a second transparentanterior plate bonded to the first transparent anterior plate.
 6. Thesystem of claim 1 further comprising: a metallic layer bonded to therear surface of the electronic display.
 7. The system of claim 1,further comprising: a fan positioned to force ambient gas along the rearsurface of the electronic display.
 8. The system of claim 1, furthercomprising: a temperature sensing device within said closed loop ofcirculating gas; a fan positioned to force circulating gas through theclosed loop; a switch in communication with said temperature sensingdevice and said fan; and wherein the fan is switched on when thetemperature within the closed loop of circulating gas reaches athreshold value.
 9. The system of claim 1 wherein: the flow of open loopambient gas is perpendicular to the flow of circulating gas in theclosed loop.
 10. The system of claim 1 wherein: the open loop ambientgas flows through the center of the closed loop of circulating gas. 11.The system of claim 1 wherein: the rear surface of the electronicdisplay is the rear surface of an LED backlight.
 12. A thermallyregulated electronic display comprising: a liquid crystal stack having adisplay surface; an LED backlight with a rear surface positionedposterior to the liquid crystal stack; a closed loop of circulating gaspositioned to surround the liquid crystal stack and LED backlight; andan open loop of ambient gas contacting the rear surface of the LEDbacklight.
 13. The electronic display of claim 12 wherein: the flow ofopen loop ambient gas is perpendicular to the flow of circulating gas inthe closed loop.
 14. The electronic display of claim 12 wherein: theopen loop ambient gas flows through the closed loop of circulating gas.15. The electronic display of claim 12 further comprising: a means fortransferring heat from the circulating gas to the ambient gas.
 16. Theelectronic display of claim 15 wherein: the means for transferring heatfrom the circulating gas to the ambient gas comprises placing thecirculating gas within a plenum and allowing ambient gas to contactexterior surfaces of the plenum.
 17. A thermally regulated electronicdisplay assembly, the system comprising: an electronic display having adisplay surface and a rear surface; a glass plate placed in front of thedisplay surface, the space between the glass plate and display surfacedefining a channel; a closed loop of circulating gas positioned tosurround the electronic display where circulating gas flows through thechannel; and an open loop of ambient gas contacting the rear surface ofthe electronic display.
 18. The electronic display of claim 17 wherein:the flow of open loop ambient gas is perpendicular to the flow ofcirculating gas in the closed loop.
 19. The electronic display of claim17 further comprising: a plenum having interior and exterior surfaceswhere the circulating gas contacts the interior surfaces and the ambientgas contacts the exterior surfaces.